#define _CRT_SECURE_NO_WARNINGS 
void strDifcat(char* dst, char* src) {
    int sz1 = sizeof(dst) / sizeof(*dst);
    int i = 0;
    int b = 0;
    int j = 0;
    int flag = 1;
    while (dst[b] != '\0') {
        b++;
    }
    sz1 = b;
    while (src[i]) {
        j = 0;
        for (int w = 0; w < sz1; w++) {
            if (dst[w] == src[i]) {
                flag = 0;
                break;
            }
        }
        if (flag != 0) {
            dst[b++] = src[i];
        }
        i++;
        flag++;
    }
    dst[b] = '\0';
}